How Can I Add a New File to a Document Library With Client Object Model?

To add a document to a document library in VB.Net:

Imports SP = Microsoft.SharePoint.Client

Public Sub LoadFileToLibrary()
    Dim clientContext As SP.ClientContext = GetYourContext()
    Dim fileContent As Byte() = GetYourByteArrayOfYourFilesContents()

    Dim fileCreationInfo As SP.FileCreationInformation = New SP.FileCreationInformation()
    fileCreationInfo.Content = fileContent
    fileCreationInfo.Overwrite = True
    fileCreationInfo.Url = "Your full destination URL here including file name"

    Dim file As SP.File
    Dim folder As SP.Folder = list.RootFolder

    file = folder.Files.Add(fileCreationInfo)
    clientContext.ExecuteQuery()
End Sub

Same classes and everything in C# too. Should be easy enough to translate this snippet.

To delete a document, you can use the same code you would use to delete a list item (because a document library is just a special type of list). You should read How to: Create, Update, and Delete List Items.

Hope this helps.

This should get you started on uploading a file in SharePoint with the Client Object Model:

http://blogs.msdn.com/b/sridhara/archive/2010/03/12/uploading-files-using-client-object-model-in-sharepoint-2010.aspx